Spool valve control for a hydraulic power boost

ABSTRACT

A control for a hydraulic power boost assembly in a braking system. Located within a housing of the boost assembly is a control piston which has a projection extending therefrom for abutting a spool valve in a valve chamber. The spool valve is responsive to movement of a brake pedal and regulates hydraulic fluid pressure to move a power piston which activates the master cylinder which in turn supplies fluid pressure to the wheel cylinders of a vehicle. The control piston is a stepped diameter piston which has one end thereof exposed to the fluid pressure in the master cylinder and the other end thereof exposed to the fluid pressure acting on the power piston. Upon manual activation by the brake pedal, the fluid pressure from the master cylinder moves the stepped control piston into engagement with the spool valve thereby preventing it from moving until the brake pedal is released. Such an arrangement prevents sudden surges of hydraulic fluid to the power piston in the power chamber which would cause an abrupt stop of the vehicle.

United States Patent [151 3,638,427

Meyers Feb. 1, 1972 [54] SPOOL VALVE CONTROL FOR A PrimaryExaminer-Edgar w-Geoghegan HYDRAULIC POWER BOOST Assistant ExaminerA. M.Zupcic Attorney-William N. Antonis and Plante, l-lartz, Smith, and

[72] Inventor: Robert E. Meyers, South Bend, Ind. Thompson [73]Assignee: The Bendix Corporation 57] ABSTRACT [22] Filed: 1970 A controlfor a hydraulic power boost assembly in a braking [21] Appl. No.: 32,241system. Located within a housing of the boost assembly is a controlpiston which has a projection extending therefrom for abutting a spoolvalve in a valve chamber. The spool valve is [52] U.S. Cll ..60/54.6responsive to movement of a brake pedal and regulates 2; v 54 5hydraulic fluid pressure to move a power piston which ac- 1 0 arc 5tivates the master cylinder which in turn supplies fluid pressure to thewheel cylinders of a vehicle. The control piston is a stepped diameterpiston which has one end thereof exposed to [56] References cued thefluid pressure in the master cylinder and the other end UNITED STATESPATENTS thereof exposed to the fluid pressure acting on the powerpiston. Upon manual activation by the brake pedal, the fluid 3,064,431 1l/ 1962 Schnell ..60/52 B pressure from the master cynnder moves thestepped control 2,853,977 9/1958 Sadler ..60/54.6 P Piston intoengagement with the Spool valve thereby prevent ing it from moving untilthe brake pedal is released. Such an FOREIGN PATENTS OR APPLICATlONSarrangement prevents sudden surges of hydraulic fluid to the 765,0791/1957 Great Britain ..60/54.6 P power piston in the power chamber whichwould cause an abrupt stop of the vehicle.

12 Claims, 2 Drawing Figures 7 -';I/ a f/4- /6 30 I v p 6 4 we s. 1/1/11 0 a "lihii A, mh!sg.\

SPOOL VALVE CONTROL FOR A HYDRAULIC POWER BOOST BACKGROUND OF THEINVENTION In prior art power boost mechanisms for braking systems whichreceive hydraulic fluid pressure from a pump operative- 1y connected tothe engine of a vehicle, when the engine is not operating, the mastercylinder must be manually activated. Upon activation, the mastercylinder alone supplies fluid pressure to the brake line. The timerequired to stop a moving vehicle is in direct proportion to the amountof force applied to the master cylinder. The force required to activatethe master cylinder is quite different without power than with power. Ifthe car engine stops during the period of deceleration, by the time thedriver adjusts to the change in applied force needed to actuate themaster cylinder, the vehicle could travel a considerable distance.During this deceleration period, if the stalled engine were startedagain with the actuating means positioned to manually activate themaster cylinder, a sudden surge of hydraulic fluid pressure would becommunicated to the power piston, thereby providing the master cylinderwith an immediate increased applied force and an instantaneous rise inbrake line pressure. With this instantaneous higher brake line pressure,the wheel brakes will abruptly stop the vehicle with possible injury toboth the occupants and vehicle with possible injury to both theoccupants and vehicle.

To prevent this sudden surge of hydraulic fluid into a brake booster, inmy copending US. Pat. application Ser. No. 17,486 [BRS-73 & 85], filedMar. .9, 1970, incorporated herein by reference and owned by the commonassignee of this application, I have provided a lever under spring loadwhich moves a sleeve to close the communication of hydraulic fluid fromthe spool valve to the power boost chamber when the engine of thevehicle is stopped. As disclosed, the control of the spool valve ismechanically responsive to a predetermined spring force.

SUMMARY OF THE INVENTION In this invention 1 have provided a power boostdevice which utilizes brake line pressure from a master cylinder tocontrol movement of a stepped diameter piston located within the powerboost device. This stepped diameter piston abuts a brake control valveand prevents movement thereof upon brake pedal application when thepressure differential between the brake line pressure and the fluidpressure in the power boost device exceeds a predetermined value uponbrake pedal application. Once the stepped piston has engaged the spoolvalve, this contact is maintained until the brake pedal is released.Upon release of the brake pedal the spool valve and stepped piston areresiliently urged against stops in the rest position.

Therefore, it is an important object of my invention to provide amechanism for sensing the loss of hydraulic fluid pressure in a brakebooster upon brake pedal application and to prevent movement of thevalve which regulates the flow of hydraulic fluid to the power pistontherein until after the operation has released the brake pedal.

It is another object of this invention to provide means for preventingabrupt stops when manual brake application is initiated prior to havinghydraulic fluid pressure available.

These and other objects will be readily apparent to those skilled in theart upon reading the specification and viewing the drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a hydraulicbrakeisystem for a vehicle with a power booster made pursuant'tomy'present invention illustrated in cross section; and

I FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1.

DETAILED DESCRIPTION In the braking system shown in FIG. 1, a pump 20supplies hydraulic fluid to both the brake booster 10 and thepowersteering mechanism 22. The brake booster 10 has a housing 12 havingan inlet port 14, an outlet port 16 and an exhaust port 18. The inletport 14 is communicated with the high-pressure side of the pump 20 whilethe outlet port 16 is in communication with the inlet of thepower-steering mechanism 22. The exhaust port 18 and the outlet portfrom the steering mechanism 22 are joined to the low-pressure side ofthe pump 20.

The brake booster housing 12 includes a bore 31 having a spool valve 30therein which moves in a manner described in US. Pat. application Ser.No. 38,088 [BRS-79-68], filed May 18, 1970, and owned by the commonassignee of this application and incorporated herein by reference. Thespool valve 30 schedules hydraulic fluid through chamber 34 to pistonmember 32 which is slidable in power chamber 33. Piston member 32 isoperatively attached to a piston 40 located in compression chamber 42 ofa master cylinder A which supplies fluid pressure to the wheel cylinders(not shown) of the vehicle through brake lines 46 and 48. Control means50 adjacent the bore 31 is connected to chamber 42 of the mastercylinder through conduit 43. Control means 50 limits the movement of thespool valve 30 in response to the difference in pressure between thehydraulic fluid pressure in the bore 31 and the fluid pressure suppliedto the brake lines 46 and 48.

More particularly, control means 50 includes a control chamber 54, whichis operatively connected to the master cylinder through the conduit 43for receiving the same fluid pressure supplied to the wheel cylinder. Astepped piston member 56 located in chamber 54 has different diameters58, 60, 62 and 64 with a stem 66 projecting from diameter 64. A pistonreturn spring 68 abuts diameter 62 while a valve return spring 70surrounds stem 66 and abuts an X-shaped stop member 72, shown moreclearly in FIG. 2.

Stepped diameter piston member 56 which extends across a vent port 174in housing 12, separates control chamber 54 from hydraulic fluid chamber74 in valve chamber 31. The section of piston member 56 having diameter58 has a groove 75 positioning ring 76 for sealing chamber 54 from thevent port 174 while diameter 62 has groove 78 positioning ring 80 forsealing chamber 74. In the event either hydraulic fluid or brake fluidwould bypass sealing rings 76 and 78, vent port 174 is opened to theatmosphere preventing the possibility of intermingling of these separateand distinct fluids. Stepped diameter piston return spring 68 isretained in hydraulic chamber 74 and biases the stepped piston to theleft, as viewed in FIG. 1, until diameter 60 abuts wall 84 in the restposition. Valve return spring 70 which surrounds stem 66 of the steppeddiameter piston member 56, has one end retained by a seat on diameter 64while the other end is held against the X- shaped stop member 72 forbiasing the spool valve 30 against stop 86, in the rest position.

MODE OF OPERATION When the engine of the vehicle is running and pump 20is in operation, high-pressure hydraulic fluid is available at inletport 14. Upon activation of the brake pedal 21 by an operator, theactivating means 52, which is of a type disclosed in US. applicationSer. No. 35,800 [BRS-69-82, 83 & 84], filed May 8, 1970, owned by thecommon assignee of the invention and incorporated by reference, movesthe spool valve to the left, as viewed in FIG. 1, causing hydraulicfluid to flow to chamber 34. This hydraulic fluid acts on power piston32 which in turn moves piston 40 in the master cylinder, therebyproviding the brake line pressure needed to stop a vehicle. At the sametime hydraulic fluid pressure passes through passages 92 of the X-shaped stop member 72, shown in FIG. 2, into hydraulic fluid chamber 74.This hydraulic fluid acts on the area of diameter 62 of the steppedpiston member 56 while the brake line pressure acts on the area ofdiameter 58. Since the piston has a larger area 62 acting with a greaterforce, the stepped piston remains seated against wall 84.

Upon stoppage of the engine, hydraulic fluid pressure is not produced bypump 20. Now, when the operator applies the brakes, manual movement ofpiston 40 in the master cylinder is required to produce the brake linepressure for stopping the vehicle. Since the control means 50 receivesthis same brake line pressure in control chamber 54, a pressuredifferential will exist across the stepped diameter member piston 56.This pressure differential will move stem 66 into engagement with theX-shaped stop member 72 to prevent the spool valve 30 from moving evenif the engine in the meantime has again been started since communicationwith inlet port 14 is now closed. Thus, asudden surge of hydraulic fluidis prevented from operating the power piston 32. Upon release of thebrake pedal the stepped piston member 56 is returned to the restposition.

I claim:

1. A hydraulic fluid power boost mechanism for energizing a mastercylinder which supplies pressure to the wheel cylinders of a vehicle,comprising:

a housing having a power chamber and a valve chamber;

piston means located in the power chamber and operatively connected tothe master cylinder;

valve means located in the valve chamber for controlling flow of fluidto said power chamber which acts on said piston means;

actuating means controlled by an operator and operatively connected tosaid valve means and said piston means;

control means operatively connected to said valve means and responsiveto the pressure in said master cylinder in the absence of pressure insaid power chamber for preventing movement of said valve means when thepressure in the master cylinder exceeds a predetermined value;

a control chamber adjacent said valve chamber; and

a stepped diameter piston located in said control means which engagessaid valve means and has one side thereof exposed to the fluid pressurein said master cylinder and the other side thereof exposed to the fluidpressure in said power chamber for limiting the operation of said valvemeans.

2. The structure, as recited in claim 1, wherein said housing includes:

a vent port located between the ends of said stepped diameter piston forpreventing mixing of the master cylinder fluid and the brake boosterfluid.

3. The structure, as recited in claim 2, which includes:

resilient means located between the stepped piston and the valve meansfor biasing said valve means against a stop in the valve chamber.

7 4. A power boost assembly for a braking system, comprising:

a housing having a power chamber and a valve chamber therein, said valvechamber being connected to a fluid pressure source;

a piston member located in said power chamber;

actuating means controlled by an operator;

valve means located in said valve chamber for regulating fluid flow fromsaid fluid pressure source to said piston member in response to movementof said actuating means;

a control chamber in the housing in communication with fluid pressure insaid braking system; and

pressure responsive means located in said control chamber andoperatively connected to said valve means, said pressure responsivemeans being exposed to and movably responsive to the pressure existingin said braking system and for limiting movement of said valve means,said pressure responsive means having a stepped diameter piston havingthe large diameter side thereof exposed to the pressure in said valvechamber and the small diameter side thereof exposed to the pressure insaid braking system so that the piston is normally urged away from saidvalve means.

5. In a power boost assembly, as recited in claim 4, wherein saidhousing includes:

a vent port located between the ends of said stepped diameter piston,which ends are sealed in said control chamber and said valve chamber,for preventing mixing of the brake system fluid and the fluid in thevalve chamber.

6. In a power boost assembly, as recited in claim 5, which includes:

a stem member connected to said stepped diameter piston;

a stop member on said valve means which permits fluid pressure to flowfrom said valve chamber to said large diameter side of said steppedpiston; and

a resilient member located between said stem member and said stop memberfor biasing said stepped diameter piston and said valve means away fromeach other and against stops in said housing.

7. In a power boost assembly, as recited in claim 6 wherein saidactuating means mechanically operates a master cylinder therebyproducing fluid pressure in said control chamber of sufficient magnitudeto move the resiliently biased stepped diameter piston into engagementwith said valve means and thereby preventing the valve means from movinguntil said actuating means is released.

8. In a power boost assembly, as recited in claim 4 wherein saidpressure responsive means includes:

a stem member having one side exposed to pressure in said valve chamberand the other side exposed to the pressure in said braking system, saidstem member engaging said valve means when the differential pressurebetween said braking system and said valve chamber is above apredetermined value.

9. In a power boost assembly, as recited in claim 8 which includes:

a resilient member located between said stem member and said valve meansfor biasing said valve means against a stop in the valve chamber.

10. In a power boost assembly, as recited in claim 9 which includes:

a master cylinder operatively connected to said actuating means forsupplying fluid to said braking system, said master cylinder uponmechanical actuation producing fluid pressure in said control chamber ofsufficient magnitude to move the resiliently biased stem member intoengagement with said valve means thereby preventing said valve meansfrom moving during mechanical activation.

11. A power booster for use in a braking system having valve means forregulating fluid pressure to piston means connected to a master cylindersupplying brake line pressure to the individual wheels of said system,comprising:

a housing having a valve bore and a piston bore, said piston means beinglocated in said piston bore, said valve means being located in saidvalve bore;

lever means connecting said valve means with said piston means;

actuating means connected to said lever means, said actuating meansbeing responsive to an operator applied force to energize said mastercylinder; and

pressure responsive means operatively I connected to said valve meansand said master cylinder, said pressure responsive means having one sideexposed to fluid pressure in said valve bore and another side exposed tobrake line pressure from said master cylinder for controlling movementof said valve means in proportion to the pressure differential acrosssaid pressure responsive means.

12. The structure as defined in claim 11, wherein said pressureresponsive means includes:

a piston member sealed in said valve bore opposite said valve means; and

a resilient member for biasing said piston member away from said valvemeans, said brake line pressure needing to overcome the force of saidresilient member and said fluid pressure in said valve bore to move saidpiston member into a limiting position with said valve means.

1. A hydraulic fluid power boost mechanism for energizing a mastercylinder which supplies pressure to the wheel cylinders of a vehicle,comprising: a housing having a power chamber and a valve chamber; pistonmeans located in the power chamber and operatively connected to themaster cylinder; valve means located in the valve chamber forcontrolling flow of fluid to said power chamber which acts on saidpiston means; actuating means controlled by an operator and operativelyconnected to said valve means and said piston means; control meansoperatively connected to said valve means and responsive to the pressurein said master cylinder in the absence of pressure in said power chamberfor preventing movement of said valve means when the pressure in themaster cylinder exceeds a predetermined value; a control chamberadjacent said valve chamber; and a stepped diameter piston located insaid control means which engages said valve means and has one sidethereof exposed to the fluid pressure in said master cylinder and theother side thereof exposed to the fluid pressure in said power chamberfor limiting the operation of said valve means.
 2. The structure, asrecited in claim 1, wherein said housing includes: a vent port locatedbetween the ends of said stepped diameter piston for preventing mixingof the master cylinder fluid and the brake booster fluid.
 3. Thestructure, as recited in claim 2, which includes: resilient meanslocated between the stepped piston and the valve means for biasing saidvalve means against a stop in the valve chambeR.
 4. A power boostassembly for a braking system, comprising: a housing having a powerchamber and a valve chamber therein, said valve chamber being connectedto a fluid pressure source; a piston member located in said powerchamber; actuating means controlled by an operator; valve means locatedin said valve chamber for regulating fluid flow from said fluid pressuresource to said piston member in response to movement of said actuatingmeans; a control chamber in the housing in communication with fluidpressure in said braking system; and pressure responsive means locatedin said control chamber and operatively connected to said valve means,said pressure responsive means being exposed to and movably responsiveto the pressure existing in said braking system and for limitingmovement of said valve means, said pressure responsive means having astepped diameter piston having the large diameter side thereof exposedto the pressure in said valve chamber and the small diameter sidethereof exposed to the pressure in said braking system so that thepiston is normally urged away from said valve means.
 5. In a power boostassembly, as recited in claim 4, wherein said housing includes: a ventport located between the ends of said stepped diameter piston, whichends are sealed in said control chamber and said valve chamber, forpreventing mixing of the brake system fluid and the fluid in the valvechamber.
 6. In a power boost assembly, as recited in claim 5, whichincludes: a stem member connected to said stepped diameter piston; astop member on said valve means which permits fluid pressure to flowfrom said valve chamber to said large diameter side of said steppedpiston; and a resilient member located between said stem member and saidstop member for biasing said stepped diameter piston and said valvemeans away from each other and against stops in said housing.
 7. In apower boost assembly, as recited in claim 6 wherein said actuating meansmechanically operates a master cylinder thereby producing fluid pressurein said control chamber of sufficient magnitude to move the resilientlybiased stepped diameter piston into engagement with said valve means andthereby preventing the valve means from moving until said actuatingmeans is released.
 8. In a power boost assembly, as recited in claim 4wherein said pressure responsive means includes: a stem member havingone side exposed to pressure in said valve chamber and the other sideexposed to the pressure in said braking system, said stem memberengaging said valve means when the differential pressure between saidbraking system and said valve chamber is above a predetermined value. 9.In a power boost assembly, as recited in claim 8 which includes: aresilient member located between said stem member and said valve meansfor biasing said valve means against a stop in the valve chamber.
 10. Ina power boost assembly, as recited in claim 9 which includes: a mastercylinder operatively connected to said actuating means for supplyingfluid to said braking system, said master cylinder upon mechanicalactuation producing fluid pressure in said control chamber of sufficientmagnitude to move the resiliently biased stem member into engagementwith said valve means thereby preventing said valve means from movingduring mechanical activation.
 11. A power booster for use in a brakingsystem having valve means for regulating fluid pressure to piston meansconnected to a master cylinder supplying brake line pressure to theindividual wheels of said system, comprising: a housing having a valvebore and a piston bore, said piston means being located in said pistonbore, said valve means being located in said valve bore; lever meansconnecting said valve means with said piston means; actuating meansconnected to said lever means, said actuating means being responsive toan operator applied force to energize said master cylinder; and pressureresponSive means operatively connected to said valve means and saidmaster cylinder, said pressure responsive means having one side exposedto fluid pressure in said valve bore and another side exposed to brakeline pressure from said master cylinder for controlling movement of saidvalve means in proportion to the pressure differential across saidpressure responsive means.
 12. The structure as defined in claim 11,wherein said pressure responsive means includes: a piston member sealedin said valve bore opposite said valve means; and a resilient member forbiasing said piston member away from said valve means, said brake linepressure needing to overcome the force of said resilient member and saidfluid pressure in said valve bore to move said piston member into alimiting position with said valve means.